首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1371篇
  免费   63篇
  国内免费   27篇
耳鼻咽喉   12篇
儿科学   29篇
妇产科学   45篇
基础医学   155篇
口腔科学   37篇
临床医学   81篇
内科学   173篇
皮肤病学   5篇
神经病学   168篇
特种医学   52篇
外科学   460篇
综合类   10篇
预防医学   30篇
眼科学   67篇
药学   77篇
肿瘤学   60篇
  2022年   18篇
  2021年   32篇
  2020年   17篇
  2019年   22篇
  2018年   21篇
  2017年   16篇
  2016年   18篇
  2015年   13篇
  2014年   30篇
  2013年   40篇
  2012年   47篇
  2011年   50篇
  2010年   28篇
  2009年   25篇
  2008年   65篇
  2007年   78篇
  2006年   69篇
  2005年   60篇
  2004年   38篇
  2003年   66篇
  2002年   49篇
  2001年   40篇
  2000年   37篇
  1999年   43篇
  1998年   13篇
  1997年   14篇
  1992年   22篇
  1991年   26篇
  1990年   27篇
  1989年   20篇
  1988年   12篇
  1987年   25篇
  1986年   20篇
  1985年   22篇
  1984年   10篇
  1983年   14篇
  1981年   9篇
  1979年   23篇
  1978年   10篇
  1976年   13篇
  1975年   12篇
  1974年   17篇
  1973年   10篇
  1972年   14篇
  1971年   21篇
  1970年   13篇
  1969年   17篇
  1968年   16篇
  1967年   12篇
  1966年   14篇
排序方式: 共有1461条查询结果,搜索用时 15 毫秒
1.
2.
The effects of spermine, spermidine and putrescine on the binding of the GABAA-benzodiazepine receptor complex were examined in the hippocampus and frontal cortex membranes of the rat. The results demonstrated modulatory effects of polyamines on the binding of diazepam and flunitrazepam but not on that of GABA, muscimol and Ro 15-1788. When membranes were prepared without detergent, the polyamines enhanced the binding of diazepam. However, while the binding capacity increased after homogenization in the presence of the non-ionic detergent Triton X-100, the polyamines did not enhance the binding but inhibited the binding of diazepam and flunitrazepam at greater concentrations. Considered together with other studies, the present findings indicate that polyamines can modulate the binding characteristics of several different neurotransmitter receptor-ionophore complexes.  相似文献   
3.
OBJECTIVE Recent evidence suggests that androstanediol glucuronide (AG), a metabolite of dihydrotestosterone (DHT) formed in skin, is frequently elevated in hirsute women, presumably reflecting enhanced 5a-reductase activity. An alternative method of demonstrating 5a-reductase activity is the androsterone (A)/aetiocholano-lone (E) ratio in urine. A and E are the 5α- and 5β- reduced metabolites, respectively, of androstenedione, which is the principal metabolite of dehydroepiandrosterone (D). Although serum AG and the urinary A/E ratio have both been considered valid methods for assessing 5α-reductase activity, the two have not been previously compared in hirsute women. The present study was undertaken to assess 5a-reductase activity in hirsute patients as determined by these two different methods. PATIENTS AND MEASUREMENTS We surveyed 47 untreated women (ages 17–33) with various degrees of hirsutism. Serum testosterone, bioavailable testosterone, dehydroepiandrosterone sulphate, and AG were determined. Additionally, A, E and D were measured in 24-hour collections of urine. RESULTS For the 47 women, 37 had elevated blood levels of AG (17.4 ± 2.2, mean±SEM; normal <8 nmol/l), but only 18 of these had an increased urinary A/E ratio (> 1.5). All but one of the remainder had elevated urinary and/or serum androgen levels. Overall, no significant correlation between AG and A/E was observed. There was a highly significant correlation between AG in serum and A in urine (r= 0.82, P<0 001). AG was also positively related to dehydroepiandrosterone sulphate (r= 0.64; P< 0.005), bioavailable testosterone (r= 0.6; P<0001), aetiocholanolone (r= 0.58; P<0 001) and total testosterone (r= 0.52; P& 0.01). In contrast, A/E was not significantly related to androgen production. CONCLUSIONS There is a poor correlation between AG and the A/E ratio in hirsute women. Although AG may be raised by increased 5α-reductase activity, it is probably also affected by the presence of elevated androgens regardless of 5α-reductase activity.  相似文献   
4.
M Frey  K Eger 《Archiv der Pharmazie》1992,325(9):545-550
2-Amino-3-cyano-dihydroindol-5-ones 2 and 3 are formed by reaction of 2-Aminopyrrole-3-carbonitriles 1 with acetylenic acid esters. In various biological test systems they behave as cytotoxic agents.  相似文献   
5.
Actinobacillus actinomycetemcomitans has been implicated in the pathogenesis of several forms of early onset and refractory adult periodontitis. Early diagnosis of colonization of the oral cavity might be of importance in order to initiate preventive measures. The aim of the present study was to determine the potential diagnostic value of oral mucosal and salivary tests to identify, among healthy young men with no or minor periodontal disease, individuals colonized by A. actinomycetemcomitans. Two hundred and one male recruits. 18–25 yr of age, took part in the present study. Mean values of periodontal parameters suggested only minor periodontal disease. Of the sites, 64.8±17.6% (mean ± SD) had a periodonta) probing depth (PPD) of 1 or 2 mm. only 1.6±2.9% deep sites of 5 mm were detected. More than 1000 subgingival and extracrevicular samples were selectively cultivated for A. actinomycetemcomitans. The organism was isolated in 55 subjects (21%). The odds for presence of at least 1 deep site of 5 mm was increased by a factor 1.99 if A. actinomycetemcomitans could be recovered. In identifying subjects colonized by A. actinomycetemcomitans. diagnostic test parameters sensitivity and predictive value for a negative test were 74.5±5.9% and 91.1±2.3%', respectively, for both saliva and dorsum of tongue samples. In contrast, pooled subgingival plaque from mesial surfaces of 1st molars was only 34.5±6.4% sensitive: the negative predictive value was 80.2±3.0%. The results point to a high diagnostic value of oral mucosal and especially saliva samples to identify young adult individuals colonized by A. actinomycetemcomitans.  相似文献   
6.
Spontaneous ovarian hyperstimulation mimicking an ovarian tumour   总被引:1,自引:1,他引:0  
Ovarian hyperstimulation syndrome in a spontaneous singletonpregnancy is exceedingly rare. We report a case of ovarian hyperstimulationpresenting as bilateral ovarian masses in association with spontaneouspregnancy, occurring in a woman with disturbed liver function.A possible mechanism is discussed.  相似文献   
7.
8.
Zusammenfassung Die cytostatische Wirkung des Sanamycin auf Milz, Thymus und Nebennieren des Kaninchens wurde mit Hilfe einer vergleichenden cyto-histologischen Untersuchungtechnik geprüft, um einen näheren Einblick in die zellspezifischen Angriffspunkte des Medikamentes zu gewinnen. Der Effekt auf die normale Lymphopoese besteht in einer zeitlich begrenzten Abnahme der reifen Lymphocyten zugunsten einer Vermehrung der Lymphoblasten, wobei histologisch eine allgemeine Reduktion der lymphatischen Gewebsanteile in Erscheinung tritt. Das RHS bleibt in diesem Zusammenhang unberührt. Die Nebennieren zeigen nach hohen Sanamycindosen Veränderungen, die einer beträchtlichen Stresswirkung oder einer reversiblen toxischen Schäidgung entsprechen können. Das durch kurzfristige Sensibilisierung stimulierte Zellsubstrat der Antikörperbildung erfährt durch Sanamycingaben eine nachhaltige Depression, während dieser Effekt bei chronisch sensibilisierten Tieren wesentlich geringer ausgeprägt ist. Die tierexperimentell erhobenen Befunde werden im Hinblick auf die therapeutische Sanamycinwirkung bei lymphatischen Systemkrankheiten und die Möglichkeiteiner Beeinflussungakuter Antigen-Antikörperreaktionen diskutiert.Herrn Professor Dr.R. Schoen zum 65. Geburtstag.  相似文献   
9.

Background

Variants in GBA are the most common genetic risk factor for Parkinson's disease (PD), and are especially prevalent in the Ashkenazi Jewish (AJ) population. However, most studies on GBA in AJ genotype only seven selected Gaucher-associated pathogenic variants rather than sequencing the whole gene, which may leave carriers of PD-associated GBA variants undiscovered.

Methods

GBA was fully sequenced using molecular inversion probes (MIPs) and Sanger sequencing in 735 AJ PD patients and 662 AJ controls, from Israel and New York. Additional AJ control data (n?=?3044) from the Inflammatory Bowel Disease Exome Portal was used.

Results

Full GBA sequencing increased the number of variants discovered by 17.4%, compared to targeted genotyping. An additional 17 PD patients were identified with GBA-associated PD. The p.E326K variant was found in 1.6% of AJ PD patients, making it the second most common PD-associated GBA variant in AJ. GBA variants were found in 18% of PD patients and 7.5% of controls (OR?=?2.7, 95%CI?=?1.9–3.8, p?<?0.0001).

Conclusion

Without full sequencing of GBA, or at minimum including p.E326K in the genotyping panel, a significant proportion of variant carriers go undiscovered and may be incorrectly assigned as non-carriers in studies or clinical trials.  相似文献   
10.
One hundred fifty-three Mycobacterium bovis strains from cattle, various animal species from zoos and wild parks, and humans were analyzed for three different genetic markers for use in the epidemiology of bovine tuberculosis. M. bovis strains isolated from cattle were found to carry a single IS6110 element, whereas the majority of strains from other animals such as antelopes, monkeys, and seals harbored multiple IS6110 elements, suggesting that the reservoirs in cattle and wild animals are separated. Because the single IS6110 element in cattle strains is located at the same chromosomal position, strain differentiation by insertion sequence fingerprinting was hampered. Therefore, we investigated the usefulness of the direct repeat and polymorphic GC-rich repeat elements for strain differentiation. Both markers allowed sufficient strain discrimination for epidemiological purposes. Evidence is presented that in Argentina, most human M. bovis infections are due to transmission from cattle, whereas M. bovis infections among humans in the Netherlands are mainly contracted from animals other than cattle. Various outbreaks of M. bovis among animals and humans are described, including a small one which likely involved transmission from human to human.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号